When working on vision with stakeholders, I like the Cover Story technique taken from the book Gamestorming.
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Each stakeholder draws the cover of a magazine (e.g., Fast Company, TechCrunch, Mashable) five years in the future, after the roadmap has been implemented. What impact has this product made on the customer base? What changes has it brought about? Make sure they include a headline, an image, a subheadline, a few sidebars, and a quote.
You can see other stakeholder tips in Chapter 8 of my book, Product Roadmaps Relaunched. Ever done this? Like? Hate? Tell me a story.